The present disclosure relates to semiconductor device manufacturing, and more particularly, to methods for spalling, i.e., removing, a material layer region of a base substrate, wherein laser ablation is used to define an edge of the material layer region that is to be spalled.
Devices that can be produced in thin-film form have three clear advantages over their bulk counterparts. First, by virtue of less material used, thin-film devices ameliorate the materials cost associated with device production. Second, low device weight is a definite advantage that motivates industrial-level effort for a wide range of thin-film applications. Third, if dimensions are small enough, devices can exhibit mechanical flexibility in their thin-film form. Furthermore, if the substrate from which a device layer is removed can be reused, additional fabrication cost reduction can be achieved.
Recent advances in spalling techniques now make it possible to remove, i.e., spall, a thin (typically less than 100 μm) semiconductor layer from an entire surface of base semiconductor substrate with near-zero thickness direction kerf losses, and to do this multiple times on the same base semiconductor substrate. The potential cost savings are enormous since (i) the thickness of the spalled semiconductor layer can be limited to the thickness needed for thin-film devices and (ii) many semiconductor layers may be derived from a single base substrate.
U.S. Patent Application Publication No. 2010/0311250 to Bedell et al. discloses a spalling process that can be employed in removing a thin semiconductor device layer from a base semiconductor substrate. The spalling method disclosed in the aforementioned publication includes depositing a stressor layer (i.e., a spall-inducing layer) on a base semiconductor substrate, placing an optional handle substrate on the stressor layer, and inducing a crack and its propagation below the substrate/stressor interface. This process, which is performed at room temperature, removes a thin layer of the base semiconductor substrate below the stressor layer. As some stages after spalling, some or all of the stressor layer can be removed utilizing an etch process.
Further improvements of spalling are needed which render spalling more efficient, controllable, and economical and thus more reliable for use in forming thin film devices.